JP2553691B2 - Luminance signal Color signal separation device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a luminance signal / color signal separation device for separating a composite image into a luminance signal and a color signal.

2. Description of the Related Art FIG. 4 is a block diagram of a conventional luminance signal / color signal separation device. In FIG. 4, 59 and 60 are comb filters, 61 is a band pass filter (BPF), 62 is a correlation detection circuit, 63 is a switching circuit, 65 is a high pass filter (HPF), 64 is a subtraction circuit, 66 Is a demodulation circuit (DEMODE).

In the conventional luminance signal / chrominance signal circuit thus configured, when the composite video signal is input from the terminal 58, it is input to the comb filter A59, the comb filter B60, and the BPF61. The comb filter A separates the carrier color signal by subtracting sample points in the vicinity of one line above the pixel of interest. The comb filter B separates the carrier color signal by subtracting the sample point one line below the sample point of interest. The BPF 61 separates the carrier color signal using pixels on the same line as the sample point of interest. Here, the output of comb filter A59 is C1, and the output of comb filter B60 is C
5. Output of BPF61 is C6. As for the positions of the sample point of interest and the nearby sample points, if the sample point of interest is S0 of one line, as shown in FIG. Sample point is l
It is the sampling point S2 of the +1 line. In the NTSC signal, since the phase of the carrier color signal is inverted for each line as shown in FIG. 5, the carrier color signal can be separated by subtracting S1 from S0 or S2 from S0. Well, terminal 58
One of the composite video signals input from the above is input to the correlation detection circuit 62. In the correlation detection circuit 62, the sample point S0 of interest
And the upper and lower sample points S1 and S2 are detected. As a method of detecting the correlation, for example, a method of comparing the absolute values of the high frequency components of each sample point, or the entire band of the sample points S0 of interest and the sample points of two lines above or below which the phase of the carrier color signal is the same There is a method of comparing the signals of. Then, the correlation detection circuit 62 outputs to the switching circuit 63 a signal indicating whether the sample point S0 of interest has a strong correlation with S1 or S2 or no correlation with either. In the switching circuit 63, if the correlation between S0 and S1 is strong, select C4 and
If S2 has a strong correlation, C5 is selected, and if S0 has no correlation with either S1 or S2, C6 is selected. Since the carrier color signal selected in this way is separated using the sample points in the vicinity that have the strongest correlation with the sample point of interest, deterioration is less likely to occur.

For example, as shown in FIG. 6 (A), when the pattern changes between the l-1 line and the l line, the correlation detection circuit 62
It is determined that the correlation between S0 and S1 is strong, and the switching circuit 63 selects the carrier color signal C4. Further, as shown in FIG. 6 (B), the pattern changes at the sample point S0, and S0 is S1 and S2.
When there is no correlation with either of the above, the switching circuit 63 selects the carrier color signal C6.

In the carrier color signal thus selected, only the high frequency component including the carrier color signal is filtered by the high pass filter 65, and subtracted from the original signal by the subtracter 64 to obtain the luminance signal.

One of the outputs of the HPF 65 is input to the demodulation circuit 66 and demodulated into two color difference signals RY and BY.

DISCLOSURE OF INVENTION Problems to be Solved by the Invention However, in the conventional luminance signal chrominance signal separation circuit configured as described above, when an oblique stripe composed of high-frequency luminance signal components as shown in FIG. 6C is input. Since there is no correlation in the vertical direction, the resolution is lowered because the luminance signal and the color signal are separated by using BPF, and such a high-frequency luminance component is almost eliminated. In addition, when a small character is input, the character is separated by BPF in most cases, and the character is crushed and unreadable, which is a big problem.

In view of the above point, the present invention has an object to provide a luminance signal / color signal separation device in which the resolution does not decrease even when the vertical correlation is weak.

Means for Solving the Problems The present invention is directed to a correlation detection circuit that detects a correlation in a vertical or oblique direction of an image, a pattern determination circuit that detects an edge of a portion having no correlation, and a correlation detection circuit if there is a correlation. A luminance signal / color signal separation device comprising a control circuit for controlling a switching circuit so as to select a comb filter using pixels in the vicinity of a certain area and select a band pass filter only for edges when there is no correlation. .

Effect The present invention can reduce only the noticeable deterioration in the edge portion without lowering the resolution of the entire image by using the bandpass filter only in the edge portion even when there is no vertical or diagonal correlation. .

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a first embodiment of a luminance signal / color signal separating apparatus according to the present invention. In FIG. 1, 1 is an input terminal,
2 is a comb filter A, 3 is a comb filter B, 4 is a band pass filter (BPF), 5 is a correlation detection circuit, 6 is a switching circuit, 7 is a high pass filter, 8 is a pattern determination circuit, and 9 is A control circuit, 10 is a subtraction circuit, 11 is a demodulation circuit (DEMOD), and 12 13 14 is an output terminal.

In this embodiment, upper and lower pixels are used as neighboring pixels, but diagonal pixels may be added as neighboring pixels. Also, there is only one comb filter and bandpass
A configuration with a filter is also possible.

In the luminance signal / chrominance signal separation device configured as described above, when the composite video signal is input from the terminal 1, it is input to the comb filter A2, the comb filters B3, BPF4 and the correlation detection circuit 5. The functions of these filters and the correlation detection circuit are the same as those of the conventional luminance signal color signal separation circuit shown in FIG. The correlation detection circuit 5 outputs a signal indicating whether the sample point of interest has a strong correlation with the upper or lower sample point, or has no correlation with either. One of these signals is input to the pattern determination circuit 8. The pattern determination circuit 8 detects a pattern on a two-dimensional plane in an area having no correlation in the vertical direction and extracts only the edge portion of the pattern. The control circuit 9 outputs the optimum filter selection signal based on the outputs of the correlation detection circuit 5 and the pattern determination circuit 8. Table 1 shows the relationship between the outputs of the correlation detection circuit 5, the pattern determination circuit 8 and the control circuit 9.

In the color signal thus selected, the high frequency component is extracted by HPF7 and two color difference signals RY and B are obtained by DEMOD11.
Demodulated to -Y. One of the outputs of HPF7 is input to the subtractor and subtracted from the original signal to obtain the luminance signal.

In this way, by using the BPF only for the slanted edges where the deterioration of the comb filter is most noticeable, it is possible to maintain the resolution of the comb filter for the entire image and eliminate the deterioration at the slanted edges.

Next, referring to FIG. 2 and FIG. 8 will be described in detail.

FIG. 2A shows the configuration of the pattern determination circuit.
It is divided into two parts, 16 pattern judgment circuits (1) and 17 pattern judgment circuits (2). FIG. 2B shows the configuration of the pattern determination circuit (1), 19 is an input terminal,
20, 21, 22, 23, 24 are 1-bit 1-line delay units (1H
DEL), 25 is a logical operation circuit (1) 26, 27, 28, 29, 30 is a 1-bit 1-clock delay device (D), 31 is a logical product circuit,
32 is an output terminal.

In the pattern determination circuit (1) configured as described above, when a correlation signal of "1" is input from the terminal 19 when there is no vertical correlation, 1H ・ DEL20, 1H ・ DEL21, 1H ・
The DEL22, 1H • DEL23, 1H • DEL24 are successively input to obtain the correlation signals for 6 lines. The input correlation signal is S
1, 1H ・ DEL20 output is S2, 1H ・ DEL21 output is S3 1H ・ D
The output of EL22 is S4, the output of 1H • DEL23 is S51H, and the output of DEL24 is S6. These correlation signals S1, S2, S3, S4, S5, S6 are input to the logical operation circuit (1). In this logical operation circuit (1), for example, the operation of the following first equation is performed.

R1 = NOT (S1 AND S6) AND ((S2 AND S3) OR (S3 AND S4) OR (S4 AND S5)) (1) And R1 which is the output of the logical operation circuit (1) is D26, D27,
These signals are input to D28, D29, and D30 one after another to obtain signals for 6 clocks. Here, the output of D26 is RD1 and the output of D27 is RD2, D28
The output of is RD3, the output of D29 is RD4, and the output of D30 is RD5. In the AND circuit, for example, the operation of the following second equation is performed and RO
Output 1

RO1 = RD1 AND RD2 AND RD3 AND RD4 AND R (2) Next, the function of the pattern determination circuit (1) will be described with reference to FIGS. 3 (A) and 3 (C). Fig. 3 (A) shows 6 lines * 7
The pattern of the block having the size of the sample point and the correlation signal are shown. The brightness and color are different at the top and bottom of the pattern at the boundary of the thick diagonal line near the horizontal in the figure. Therefore, there is no vertical correlation in the vicinity of the thick diagonal line, and the range is the range indicated by the diagonal line. The line of this block is L + 2 line from L-2 line, A1 to A7 B1 to B7, C1 to C
7, D1 to A7, E1 to E7 and F1 to F7 are the correlation signals for each line. In this correlation signal, the white circle is "0" (with vertical correlation) and the black circle is "1" (no vertical correlation), so the shaded area is a black circle and the other areas are white. It becomes a circle.

FIG. 3C also shows the correlation signal of the pattern of the block of 6 lines * 7 sample points. In FIG. 3 (C), there is almost no vertical correlation in the block and no edge exists. Therefore, most of the correlation signals are black circles and white circles are mixed in places. First, the case where the correlation signal of FIG. 3A is input to the pattern determination circuit (1) 16 will be described.

When the inputs S1, S2, S3, S4, S5, S6 to the logical operation circuit (1) 25 are a set of correlation signals composed of A7, B7, C7, D7, E7, F7 of FIG. 3 (A), respectively. , A7 and F7 are "0" and B1 and C7 are "1" consecutively, and the output R1 is "1" from the equation (1). Also, the set of correlation signals A6, B6, C6, D6, E6,
Even when F6 is input to the logical operation circuit (1) 25, the output R1 becomes "1". Further, when a set of correlation signals up to 6 clocks before is input, the output R1 becomes "1" similarly.

Therefore, the outputs RD1, RD2, RD3, RD4, RD5 of D26, 27, 28, 29, 30 in FIG. 2B are all "1", and the output of the AND circuit is also "1". The edge of FIG. 9A is detected.

Next, the case where the correlation signal of FIG. 3C is input to the pattern determination circuit (1) 16 will be described.

Input signal 1, S2, S3, S4, S5, S6 to the logical operation circuit (1) 25
Is the set of correlation signals A7, B7, C7, D7, E of FIG. 3 (C), respectively.
When it is 7, F7, the output R1 is “0” from the equation (1). However, when the set of correlation signals A6, B6, C6, D6, E6, F6 one clock before is input to the logical operation circuit (1) 25, the output R1 becomes "1". However, when a set of correlation signals from 2 clocks to 6 clocks before is input, the output signal becomes "0". Therefore, RD1 becomes "1", but RD2, RD3, RD4, RD5 become "0", the output of the AND circuit 31 becomes "0", and no edge is detected.

In this way, the pattern determination circuit (1) 16 uses the correlation signal to perform the operation shown in the equation (1) by the logical operation circuit (1) 25 to detect the vertical edge pattern at each sample point. By delaying in the horizontal direction and determining that the edge pattern is continuous when the edge pattern for several clocks is continuous, it is possible to detect an edge close to horizontal as shown in FIG. 3 (A). Further, as shown in FIG. 3C, when there is no vertical correlation but it is not an edge, it is judged that there is an edge at a certain sample point, but since the AND circuit 31 checks the horizontal continuity, a false detection is made. Is prevented.

Next, the pattern determination circuit (2) 17 shown in FIG. 2C will be described. In FIG. 2 (C), 33 is an input terminal, 34, 35,
36, 37, 38, 39 are 1-bit 1-clock delay devices (D), 40 is a logical operation circuit (2), 41, 42, 43, 44 are 1
A bit delay line (1H • DEL), 45 is an AND circuit, and 46 is an output terminal. When the correlation signal is input to the pattern determination circuit (2) 17 configured as described above, D3
The signals are sequentially input to 4, 35, 36, 37, 38 and 39 to obtain a correlation signal for 7 clocks. The correlation signal input here is
S12, D34 output is S22, D35 output is S32, D36 output is S42, D
The output of 37 is S52, the output of D38 is S62, and the output of D39 is S72. In the logical operation circuit (2) 40, for example, the operation of the following third equation is performed and R2 is output.

R12 = NOT (S12 OR S72) AND ((S22 AND S32) OR (S32 AND S42) OR (S42 AND S52) OR (S52 AND S62)) …… (3) R12 is 1H ・ DEL41, 42, 43, 44 It is input one after another. 1H ・ DEL41 output is RD12, 1H ・ DEL42 output is RD22H
・ The output of DEL43 is RD32 and the output of 1H ・ DEL44 is RD42.
These signals are input to the logical product circuit 45 and, for example, the following fourth
Expression calculation is performed.

RO2 = (RD12 AND RD22 AND RD32 AND RD42) (4) Next, the function of the pattern determination circuit (2) will be described with reference to FIGS. 3 (B) and 3 (C). FIG. 3 (B) is also FIG. 3 (A).
In the same manner as the above, the pattern of the block having the size of 6 lines * 7 sample points and the correlation signal are shown. The brightness and color are different between the left and right sides of the pattern at the boundary of the thick diagonal line near the vertical in the figure. Therefore, there is no correlation in the horizontal direction near the thick diagonal line, and the range is the range indicated by the diagonal line. The line of this block is L + 2 line from L-2 line, A1 to A7, B1 to B7, C1 to C7, D1 to A7, E1 to E7 and F1 to F7 represent the correlation signals in each line. In this correlation signal, the white circle is "0" (with vertical correlation) and the black circle is "1" (no vertical correlation), so the shaded area is a black circle and the difference is It becomes a white circle.

The correlation signal of FIG. 3 (B) is the pattern determination circuit (2) 17
The case of being input to will be described.

Input to the logical operation circuit (2) 40 S12, S22, S32, S42, S52,
S62 and S72 are F1, F2, F3, F4, F5,
In the case of a pair of correlation signals consisting of F6 and F7, F1 and F7 are “0”
Therefore, "1" is continuous from F3 to F6, and the output R12 is "1" from the equation (3). Also, the set E of the correlation signal one line before
Even when 1, E2, E3, E4, E5, E6, and E7 are input to the logical operation circuit (2) 40, the output R12 becomes "1". Furthermore, when a set of correlation signals up to 4 lines before is input, output R1
2 becomes "1".

Therefore, 1H ・ DEL41, 1H ・ DEL42, 1H ・ in Fig. 2 (C)
RD12, RD22, RD32, RD42, RD which are the outputs of DEL43, 1H and DEL44
All of 52 are "1", the output of the AND circuit 45 is also "1", and the edge of FIG. 3A is detected.

Next, the case where the correlation signal of FIG. 3C is input to the pattern determination circuit (2) 17 will be described.

Input signals S12, S22, S32, S42 to the logical operation circuit (2) 40,
S52 and S62 are the correlation signal pairs F1, F2, and F of FIG. 3 (C), respectively.
When it is 3, F4, F5, F6, F7, the output R12 is “0” from the formula (3).
Becomes However, the correlation signal pairs E1, E2, E3,
When E4, E5, E6, and E7 are input to the logical operation circuit (2), the output R12 becomes "1". However, when a set of correlation signals from two lines before to four lines before is input, the output signal becomes "0". Therefore, RD12 becomes "1", but RD22, RD32, RD4
2 becomes "0", the output of the AND circuit 45 becomes "0", and no edge is detected.

In this manner, the pattern determination circuit (2) 17 uses the correlation signal to perform the operation shown in the equation (3) by the logical operation circuit (2) 40 to detect the horizontal edge pattern at each sample point, By delaying in the vertical direction and determining that the pattern is an edge when the edge pattern is continuous for several lines, an edge close to vertical as shown in FIG. 3B can be detected. Further, as shown in FIG. 3C, when there is no vertical correlation but it is not an edge, it is judged that there is an edge at a certain sample point, but since the AND circuit 31 checks the horizontal continuity, a false detection is made. Is prevented.

EFFECTS OF THE INVENTION As described above, according to the present invention, the correlation detection circuit detects the vertical correlation of an image, and when there is no vertical correlation, the edge of the area is detected and the edge portion is detected. By using BPF only for the image, it is possible to eliminate noticeable deterioration at the edge portion without lowering the resolution of the entire image, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a luminance signal / color signal separating apparatus of the present invention, FIG. 2 is a block diagram of a pattern determining circuit of the same embodiment, and FIG. 3 is an operation of the pattern determining circuit 8. FIG. 4 is a block diagram of a conventional luminance signal / color signal separation circuit, FIG. 5 is a signal diagram in the circuit, and FIG. 6 is a configuration diagram showing a design. 1 ... input terminal, 2 ... first comb filter, 3 ... second comb filter, 4 ... BPF, 5 ... correlation detection circuit,
6 ... Switching circuit, 7 ... HPF, 8 ... Pattern determination circuit, 9 ... Control circuit, 10 ... Subtraction circuit, 11 ... Demodulation circuit (DEMOD), 12, 13, 14 ... Output terminal, 16 ...... First pattern judgment circuit, 17 ...... Second pattern judgment circuit, 2
0, 21, 22, 23, 24, 41, 42, 43, 44 …… 1H delay memory (1H ・ DEL), 26,27,28,29,30,34,35,36,37,38,39… … 1
Clock delay memory (1D), 25 ... Logical operation circuit 1, 40
... Logical operation circuit 2, 31, 45 ... AND circuit.

Claims (3)

(57) [Claims] 1. A plurality of comb filters and band pass filters using neighboring pixels in a vertical or diagonal direction with respect to a pixel of interest, switching means for switching outputs of these filters, and a vertical filter or a diagonal filter with respect to the pixel of interest. Correlation detection means for detecting the correlation with neighboring pixels, pattern determination means for detecting a portion which has no correlation with neighboring pixels and is an edge of a pattern based on the output of the correlation detection means, and the correlation detection When there is a correlation based on the output of the means, a control means for controlling the switching means so as to select a comb filter using pixels in the vicinity of the correlation and to use the bandpass filter only for the edges of the portion having no correlation A luminance signal / color signal separation device comprising: 2. A plurality of one horizontal period delay means for delaying a correlation signal indicating the presence / absence of correlation between a pixel of interest and a neighboring pixel, and the correlation using the outputs of these one horizontal period delay means as inputs. A first logical operation means for detecting a vertical width of a portion without a signal and outputting a signal when the width is equal to or less than a predetermined width; and a plurality of delay means for delaying an output of the first logical operation means in the horizontal direction, 2. The luminance signal according to claim 1, further comprising a first pattern judging means which is a logical product means for checking the continuity of the output signal of the first logical operation means with the outputs of these delay means as inputs. Color signal separation device. 3. A plurality of delay means for delaying a correlation signal indicating the presence / absence of correlation between a pixel of interest and a neighboring pixel, and a horizontal direction of a portion having no correlation with outputs of these delay means as inputs. Second logical operation means for detecting the width of the signal and outputting a signal when the width is less than a certain width, a plurality of one horizontal period delay means for delaying the output of the second logical operation means in the vertical direction, and these one horizontal 2. The luminance signal color according to claim 1, further comprising a second pattern judging means which is constituted by a logical product means for inputting an output of the period delay means and for checking continuity of an output signal of the second logical operation means. Signal separation device.